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IS 5553-3 (1990): Reactors, Part 3: Current limitingreactors and neutral earthing reactors [ETD 16:Transformers]

IS 5553 ( Part 3 ):1990

Indian Standard

REACTORS - SPECIFICATION PART 3 CURRENT-LIMITING REACTORS AND NEUTRAL EARTHING REACTORS

( First Revision )

First Reprint JANUARY 1994

UDC 621’316’935

0 BIS 1990

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

September 1990 Price Cramp 3

Transformers Sectional Committee, ETD 16

FOREWORD

ThisIndian Standard ( Part 3 ) ( First Revision ) was adopted by the Bureau of Indian Standards on 18 January 1990, after the draft finalized by the Transformers Sectional Committee had been approved by the Electrotechnical Division Council.

This standard was first published in 1970. This revision has been undertaken with a view to bringing it in line with the revision of IEC Pub. 289 - 1988 ‘Reactors’, issued by the International Electrotechnicai Commission ( IEC ).

In this revision, the requirements for reactors have been covered in eight parts as follows:

Part 1 : Part2: Part3: Part 4 : Part 5 : Part 6 : Part7: Part 8 :

General Shunt reactors Current limiting and neutral earthing reactors Damping reactors Tuning reactors Earthing transformers (neutral couples ) Arc suppression reactors Smoothing reactors

This standard ( Part 3 ) has been based on IEC Pub 289 ( 1988 ) ‘Reactors ( Second Edition, 1988 ), Section Three, ‘Current-limiting reactors and neutral-earthing reactors’, issued by the International Electrotechnical Commission ( IEC ).

This part shall be read in conjunction with Part 1 of this standard. A list of referred standards is also given in Part 1 of this standard.

In this standard, references has been made to IS 2026 ( Parts 1 to 4 ) transformers* which is, therefore, a necessary adjunct to this specification.

specification for ‘power

The reactors meant for continuous duty may be overloaded under certain conditions. In the absence of any Indian Standard guide on the subject at present, this aspect may be checked with the manufacturer.

Indian

REACTORS -

IS 5553 ( Part 3 ) : 1990

Standard

SPECIFICATION PART 3 CURRENT-LIMITING REACTORS AND NEUTRAL EARTHING REACTORS

( First Revision ) 1 SCOPE

1.1 This standard ( Part 3 ) applies to reactors intended for limiting the current under-system fault condition, such as:

a) Current Limiting Reactors

Reactors intended for limit:ng the short time current and during normal opera- tion, a continuous current flows through the current limiting reactor.

b) Neutral-Earthing Reactors

Single-phase reactors for three-phase system, connected between the neutral of a system and earth, for limiting the line-to-earth current under system fault conditions_. Neutral earthing reactors generally carry no, or only a small continuous current.

1.1.1 Depending on their application, reactors for other purposes may also be covered in this section.

These reactors are, for example:

a) Load sharing reactors for balancing the current in parallel circuits, and

b) Starter reactors connected in series to an ac motor for limiting the starting current.

1.1.2 Design

With regard to design and installation, current- limiting reactors may be classified as:

a) Single-phase or three-phase,

b) Dry-type or oil-immersed type,

c) With air core or without gapped iron core, and

d) With or without shield:

1) With or without taps, and: 2) For indoor or outdoor installation.

NOTE 1 The magnetic shield of current-limiting reactor is generally designed to be saturated when the reactor carries a high short-time current.

2 Since an unshielded dry type current-limiting reactor generates a high magnetic stray field when it carries a high short-time current, the location of the phase windings and their location-relative to other apparatus and to metallic structures shall be considered with a view to minimizing possible effects, such as, undue heating of adjacent metallic parts or dangerous forces on them during short- time current.

2 REFERENCES

2.1 The Indian Standards listed in Annex A of Part 1 of this standard are necessary adjuncts to the standard.

3 TERMINOLOGY

3.0 For the purpose of this standard ( Part 3 ), the following definitions shall apply.

3.1 Rated Continuous Current, IN

The current at rated frequency flowing through the terminals of the winding which the reactor is designed to carry continuously. Unless other- wise specified, no rated continuous current ia specified for neutral-earthing reactors.

3.2 Rated Short-Time Current, IKN

The rms value of the steady-state symmetrical component of the short-time current at rated frequency to be carried for a specified duration for which the reactor is designed and which the reactor may withstand without undue heating or excessive mechanical stresses.

NOTE - The rated short-time current is derived from system fault conditions.

3.3 Rated Short-Time Current Doration, tKN

Duration of the rated short-time current for which the reactor is designed.

3.4 Rated Impedance, ZXN

The specified impedance in ohms per phase at rated frequency and rated short-time current.

3.4.1 For a three-phase current-limiting reactor or three-phase bank of single-phase reactor, the rated impedance is the average of the three single-phase impedances.

NOTE - In a three-phase current-limiting reactor, or a bank of single-phase reactors, the magnetic coupling between phases causes the virtual imped- ance per phase to be different from the rated impedance as defined above. This is of minor practical importance if the coupling factors are below 5 percent.

4 INSULATION LEVEL

4.1 The provisions of IS 2026 ( Part 3 ) : 1981 shall apply.

4.2 Insulation Requirements for Corrent-Limiting Reactors The insulation requirements between phases and to earth shall generally correspond to the highest

1

IS 5553( Part 3 ) : 1990

voltage of equipment U, of the system in which the reactor is to be installed. The insulation requirements across the winding may be specified lower, particularly if surge arresters are connect- ed in parallel -with the winding. It is recom- mended that the rated voltage of the surge arrester is selected not less than 1.2 times the voltage developed across the reactor by the rated short-time current.

4.3 Insulation Requirements for Neutral Eartbing Reactors

The insulation requirements of a neutral earthing reactor shall correspond to insulation of the neutral of the system in which the reactor is to be installed. For the-earth terminal, the selec- tion of a reduced insulation level may be appro- priate ( non-uniform insulation ).

;;;;y;Ty TO WITHSTAND SHORT-TIME

5.1 The current limiting reactors and neutral- earthing reactors shall be designed to withstand the thermal and dynamic effect of the rated short-time current and for the rated short-time current duration.

6 RATINGS

6.1 Rated Continuous Current

Unley otherwise specified, the rated continuous current is a symmetrical three-phase current.

6.2 Rated Short-Time Current

The rated short-time current shall be specified not less than the highest value of current under recognized system fault conditions.

6.3 Rated Short-Time CurrentDnration

Unless otherwise specified, the short-time current duration shall be for:

a) Current limiting reactors : 2 seconds, and

b) Neutral-earthing reactors: 10 seconds.

6.4 Rated Impedance

NOTE -If several successive faults may occur within a short period of time, the duration, the interval 6f time between applications, and the number of applications shall he spectfled by the purchaser. The rated short-time duration shall be selected accordingly.

The value of rated impedance shall be specified together with the rated short-time current in accordance with the system parameters and the recognized cases of system faults. This quantity has the character of a necessary minimum value. For a reactor with magnetic shield, the impe- dance for continuous current shall also be stated by the manufacturer, be measured, and shall be given on the nameplate.

For a three-phase reactor, or a bank of separate reactors with defined installation, the manu-

facturer shall, on request, supply information on the coupling factors or mutual reactances between phases under short-time current con- ditions.

NOTE - For certain types of reactors, direct measurement of this quantity is difficult ( see 9.11 ).

7 TEMPERATURE-RISE

7.1 Temperatore-Rise ‘at Rated Continuous Current

The temperature-rise limits given in 3 of IS 2026 ( Part 2 ) : 1977 and IS 11171 : 1985, shall apply.

7.2 Temperature after Shbrt-Time Current Loading

The temperature of the winding after short-time current loading shall not exceed the values pres- cribed for transformer windings under short- circuit conditions in 9.1.4 of IS 2026 ( Part 1 ) : 1977.

8 RATING PLATES

8.1 Each reactor shall be~provided with a rating plate of weather-proof material, fitted in a visible position, showing the appropriate items indicated below. .

The sentries on the plate shall be indelibly marked ( for example, by etching, engraving or stamping ).

8.1.1 Information to be given in all cases:

a) Type of reactors,

b) 4 d) 4 f) g) h) 3 k)

m> 4

Number of this specification*

Indication of the source of manufacture

Manufacturer’s serial number,

Year of manufacture, Highest voltage of equipment, Insulation level, Rated frequency, Number of ~phases, Impedance ( measured value ) ( at rated continuous current ), Rated continuous current, Rated short-time current and specified duration,

p) Type of cooling, q) Total mass, r) Mass of insulating oil, s) Mass of core atid winding assembly, and t) Temperature-rise in oil for which the

reactor is designed.

8.1.2 Additional information to be given in certain cases:

a) Temperature class of insulation ( for dry- type reactors );

b) Temperature rise ( if not a normal value );

3

IS 5553 ( Part 3 ) : 1990

4

4

f)

Ii9 h)

Insulation requirements for the earth terminal of winding with non-uniform insulation;

Rated lightning impulse withstand voltage across the winding when surge arresters are connected in parallel with the wind- ing ( for current-limiting reactors );

Transportation mass ( for reactors exceed- ing 5 t total mass );

Untaking mass ( for reactors exceeding 5 t total mass >;

Insulating liquid, if not mineral oil; and

Details regarding tappings, if any.

9 TESTS

9.1 For general requirements for type, routine and special tests, the provision of 16.1 of IS 2026 ( Part 1 > : 1977, shall apply.

9.2 Type Tests

The following shall constitute the type tests:

a) Measurement of winding resistance [ see 16.2 of IS 2026 ( Part 1 ) : 1977 1;

b) Measurement of insulation resistance [ see 16.6 of IS 2026 ( Part 1 ) : 1977 1;

c) Measurement of impedance of continuous current if applicable ( see 9.5 );

d) (&;,,rrent of loss, if applicable . . ;

e) Separate-source voltage withstand test ( see 9.7 );

f) Induced overvoltage withstand test ( see 9.8 );

g) Measurement of insulation resistance [ see 16.6 of IS 2026 ( Part 1 ) ; 1977 1;

h) Temperature-rise test at rated continuous current ( see 9.9 ); and

j) Lightning impulse test ( see9.10 ).

9.3 Routine Tests

The following shall constitute routine tests:

4

b)

4

4

Measurement of winding resistance [ see 16.2 of IS 2026 ( Part 1 ) : 1977 1;

Measurement of insulation resistance [ see 16.6 of IS 2026 (Part 1 ) : 1977 1; Measurement of the impedance of conti- nuous current, if applicable ( see 9.5 ); Measurement of loss, if applicable ( see 9.6 ); and

e) Separate-source voltage withstand test ( see 9.7 );

f) 19n$ced overvoltage withstand test ( see . .

9.4 Special Tests

The following shall constitute the special tests:

a) Short-time current test and measurement

of impedance at short-time current ( see 9.11 >; and

b) Measurement of acoustic sound level ( see 9.12 ).

9.5 Measurement of the Impedance at Contiau- ous Current

9.5.1 The impedance shall be measured at rated frequency. For single-phase reactors and three- phase banks of single-phase reactors, the impe- dance shall be measured at single-phase excita- tion and the impedance is the average of three single-phase impedances.

9.5.2 The impedance of a three-phase reactor where the magnetic coupling factors are higher than 5 percent shall be measured by applying a system of symmetrical voltages to the star-con- nected phase windings.

9.5.3 The impedance shall then be taken as:

Line-to-line applied voltage Average measured current -7

NOTE -For reactors without magnetic shield, this test shall also verify the rated impedance.

9.6 Measurement of Loss

9.6.1 This measurement applies only on reac- tors where a continuous current is specified. The measurement shall be done -at rated fre- quency.

9.6.2 The method for determination of loss is subject to agreement, satisfactory documenta- tion regarding accuracy and reliability of the proposed method shall be provided.

9.6.3 As the power factor of a current-limiting reactor is normally very low, loss measurement using conventional wattmeter methods may be subject to considerable errors.

9.6.4 A bridge method may be used to advant- age.

9.6.4.1 For reactors without magnetic shield, the measurement may be made at any current and corrected to rated continuous current. For temperature correction, refer to 16.4 of IS 2026 ( Part 1 ) : 1977.

9.6.4.2 For reactors with magnetic shield, the lossin the various parts of the reactor ( laR loss, iron loss and additional loss ) may not be sepa- rated by measurement. It is thus preferable, in order to avoid corrections to reference tempe- rature, to perform the measurement when the average temperature of windings is practically equal to the reference temperature.

This measurement may be made during the temperature-rise test, fo;J example.

If several units are to be tested, it is recom- mended that the unit which receives loss measurement as a type test at nearly reference temperature shall be measured at ambient

3

IS S553 ( Part 3 ) : 1990

temperature also. Remaining units shall then be measured at ambient temperature only and their loss figure shall be corrected to reference temperature by the same ratio as measured on the type-tested unit.

9.7 Separrte Source Voltage Withstand Test

9.7.1 The test shall be generally carried out in accordance with 10 of IS 2026 ( Part 3 ) ; 1981.

9.7.2 The test voltage shall be applied:

a) between each winding t and earth, and

b) between different windings.

9.8 InducedOvervoltage Withstand Test

9.8.1 The test shall be performed in accordance With 11.1 of IS 2026 ( Part 3 ) : 1981. The test voltage shall be twice the voltage occurring across the winding at rated‘short-time current.

9.8.2 If the power and the voltage requirements for this test exceed those available at the test station, the test shall be replaced by agreement between the purchaser and the manufacturer by a lightning impulse test.

9.9 Temperatare-Rise Test at Rated Continuous Current

The test shall be generally carried out in accor- dance with IS 2026 ( Part 2 ) : 1977.

9.9.1 Dry- Type Reactors

9.9.1.1 The test shall be carried out at a value of test current as near as possible to the rated current IN and not less than 90 percent of this value and the run continued until the tempera- ture rise increment of any part of the reactor is less than 2°C in 1 hour.

9.9.1.2 The temperature-rise of the winding above the temperature of the cooling air for rated current, A BN is calculated from the formula:

A~N = be, q L- 1

P t where

IN = rated continuous current,

II = test current, and

A& = temperature rise at test current.

The value of q shall be taken as:

AN cooled reactors = 1’6, and

AF cooled reactors = 1’8.

The temperature 0, of the winding shall be calculated from its measured resistance accord- ing to 4.6 of IS 2026 ( Part 2 ) : 1977.

9.9.2 Oil Immersed Type Reactors

The determination of top oil temperature rise and of winding temperature rise shall be made in accordance with 4 of IS 2026 ( Part 2 ) : 1977.

9.10 Lightning Impulse Test

9.10.1 For general information, refer to I2 of IS 2026 (Part 3 ) : 1981 and IS 11171 : 1985.

9.10.2 Current -Limiting Reactors

The test voltage is applied to each terminal of the tested winding in turn while the other ter- minal is earthed. The terminals of the other windings shall also be earthed. If reduced insulation requirements .across the winding are specified, the lightning impulse test procedure shall be subject to agreement between purchaser and manufacturer.

9.10.3 Neutral-Earthing Reactors

For neutral-earthing reactors, the test voltage is applied to the terminal which is to be connected to the transformer neutral whereas the other terminal is earthed. The duration of the front time may be in?reased up $0 13 seconds.

NOTE - The correct time to half value may not be achievable. This should normally be accepted.

9.11 Short-Time Current Test and Measurement of Impedaoce of Short-Time Current

9.11.1 For general information, IS 2026~( Part 1 ): 1977 applies. The short-time current test is designed to prove the mechanical capability at rated short-time current and, in the case of a reactor with magnetic shield, to permit measure- ment of the rated impedances.

9.11.2 Unless otherwise specified, the first peak of short-time current shall have a peak value of 1’8 x flZ_ times the rms value (Certain service conditions may result in asymmetry factor different from 1’8 X ,f_Z ).

9.11.3 From the records of the symmetrical values of test voltage and current, the impedance at short-time current shall be determined. Its value shall be equal to the rated impedance within the appropriate tolerance.

9.11.4 For a three-phase reactor, three single- phase impedance values shall be determined from the single-phase current applications. Their arithmetical average value shall apply.

9.11.5 For a three-phase reactor, three single- phase impedance values shall be determined from the single-phase current applications. Their arithmetical average value shall apply.

9.11.6 During the tests; the induced voltages in non-tested phases shall be recorded, in order to determine coupling factors or mutual impe- dances between phases.

9.11.6.1 Test procedure

For single-phase reactors, the test shall consist of two applications of rated short-time current of duration 0’50 B 0’05 .seconds.

4

IS 5553(Part3):1990

the purchaser.

10 TOLERANCES

10.1 Tolerances of the impedance established by test and/or calculation at rated short-time current shall be:

a) +20 percent, and b) -0 percent of rated impedance.

In case of three phase reactors, the current mea- sured in each phase winding under the condi- tions~defined in 9.5, shall not deviate by more than 5 percent from the average value but the impedance per phase shall al;v$s be within the

above mentioned range of _., percent.

Tolerances for impedance at continuous current,

if stated, shall be ‘r percent.

Tolerance on loss ( only with a continuous current is assigned to the reactor ) shall be f15 percent of the declared value.

Three-phase reactors, or a bank of separate reactors with defined installation, shall be sub- mitted to one single-phase test for each phase with full asymmetry, and to one three-phase test with approximately equal three-phase current.

NOTE - If the duration 05 seconds may not be obtained during test because of insufficient power capacity of the test equipment. shorter durations are subject to agreement between the purchaser and the manufacturer.

9.11.2 Thermal Behaviour at Short-Time Current

9.11.2.1 The thermal short-time withstand capa- bility shall be demonstrated by calculation accor- ding to 9.1 of IS 2026 (Part 1 ) : 1977.

NOTE - This calculation leads to conservative result for long rated short-time current duration.

9.12 Measurement of Acoustic Sound Level

The method of test and criteria for conformity shall be agreed between the manufacturerand

5

-.. _~ --- .._.__ .-

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Dot : No. ETD 16 ( 2776)

Amendments Issued Since Publication

Amend No. Date of Jssue Text Affected

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